I wish to do a full outer join between two tables A, B joining on A.ID = B.ID. Now, it is quite easy to include A.ID and B.ID in a result set. this will include rows where:
- A.ID is null, B.ID is not null
- B.ID is null, A.ID is not null
- A.ID and B.ID have the same value.
I want to have a third column which be equal to:
- A.ID and B.ID when they are the same value
- A.ID when A.ID has a value and B.ID is null
- B.ID when B.ID has a value and A.ID is null
How do I do this?